Light (and other forms of electromagnetic radiation) CAN travel through
solids, liquids, and gases, but it doesn't NEED anything to travel through.
It can travel just as easily through complete vacuum. That's how the heat
and light of the sun reach us.
Sound NEEDS something to travel through. If there's nothing there, then
sound doesn't travel at all. It can be solid, liquid, or gas, but there HAS TO
BE something there. Otherwise sound doesn't go anywhere. Not even an inch.
